1. Field
The presently disclosed subject matter relates to a semiconductor light source apparatus, and more particularly to a high power semiconductor light source apparatus including a phosphor layer, which can prevent a reduction of brightness absorbed by an adhesive material, and which can emit various color lights having a large amount of light intensity in order to be able to be used for general lighting, a stage light, a street light, a projector, etc.
2. Description of the Related Art
Semiconductor light source apparatuses that emit various color lights by combining a phosphor layer with a semiconductor light-emitting device such as an LED have been used for business machines, home electronics, audio instruments, etc. Recently, because brightness of the semiconductor light source apparatuses have improved, a range of application for the semiconductor light source apparatuses has expanded to fields such as general lighting, street lighting, a vehicle headlight, etc.
One method for improving the brightness of the semiconductor light source apparatuses including the phosphor layer, includes providing an excitation intensity of the phosphor layer that is enhanced by flowing a large current in the semiconductor light-emitting device. However, because heat occurs in the phosphor layer due to the large current, a transparent resin contained in the phosphor layer can be tarnished. Because the transparent resin is mixed with a phosphor in the phosphor layer, the tarnish of the transparent resin results in absorption of a part of light excited by the phosphor layer, and therefore may cause a reduction of the excitation intensity.
In addition, a reduction of a fluorescent intensity may be caused by a thermal quenching property of the phosphor layer due to the large current. The thermal quenching property is a phenomenon in which a fluorescent intensity of a phosphor becomes reduced when the phosphor is heated at a high temperature. Therefore, because the tarnish of the transparent resin and the reduction of the fluorescent intensity cause a reduction of a light-emitting intensity in semiconductor light source apparatuses that include a phosphor layer, it is difficult to improve the brightness of the semiconductor light source apparatuses by simply flowing a large current.
To improve such a problem, a semiconductor light source apparatus using a phosphor layer that includes a phosphor particle without a transparent resin is disclosed in Patent Document No. 1 (Japanese Patent Application Laid Open JP2012-064484). FIG. 5 is a schematic structural view showing a conventional semiconductor light source apparatus including a phosphor layer, which is disclosed in Patent Document No. 1.
The conventional semiconductor light source apparatus 20 includes a semiconductor light source 11; a phosphor ceramic layer 12 including a phosphor particle without a transparent resin; a light-reflecting substrate 13 mounting the phosphor ceramic layer 12 via an adhesive layer 14; and a lens 16 being located in a light-reflecting direction of a mixture light 15, in which a part of direct light emitted from the semiconductor light source 11 is mixed with a wavelength converted light through the phosphor ceramic layer 12 by an excitation light (another part of direct light) emitted from the semiconductor light source 11.
The phosphor ceramic layer 12 may not basically include a transparent resin, and therefore a tarnish of the phosphor ceramic layer 12 may not occur. In addition, because the phosphor ceramic layer 12 is made of a material having a low thermal sensitivity, a thermal quenching may be prevented. Consequently, it may be possible for this semiconductor light source apparatus to improve brightness by simply flowing a large current therethrough.
In the conventional semiconductor light source apparatus 20, the phosphor ceramic layer 12 is attached on the light-reflecting substrate 13 by the adhesive layer 14 such as an adhesive material, a metallic solder (e.g., silver solder), etc. The light-reflecting substrate 13 is operated as a reflective surface for the part of direct light emitted from the semiconductor light source 11 and the wavelength converted light through the phosphor ceramic layer 12 by the excitation light, a metallic heat sink for radiating heat generated from the phosphor ceramic layer 12, and an attachment member for attaching the phosphor ceramic layer 12.
Accordingly, when the phosphor ceramic layer 12 is attached on the light-reflecting substrate 13 by the adhesive material 14 such as a resin adhesive and the like, which have a low thermal conductivity as compared with a metallic material, the heat generated from the phosphor ceramic layer 12 may not radiate in an efficient manner. Especially, when the mixture light 15 having a high light-emitting brightness is emitted toward the lens 16 by entering a large amount of light such as a laser light into the phosphor ceramic layer 12, which is formed in a small shape, the phosphor ceramic layer 12 may break because the heat generated from the phosphor ceramic layer 12 cannot appropriately radiate from the light-reflecting substrate 13.
By contrast, when the phosphor ceramic layer 12 is attached on the light-reflecting substrate 13 by the metallic solder such as a silver solder, the solder material tends to easily spread toward a side surface of the phosphor ceramic layer 12. When the solder material spreads toward the side surface of the phosphor ceramic layer 12, because the solder material, which is attached to the side surface of the phosphor ceramic layer 12, may absorb light emitted from the side surface of the phosphor ceramic layer 12, said absorbed light may become a negative factor for reducing a light-emitting efficiency of the semiconductor light source apparatus 20.
The above-referenced Patent Documents and additional Patent Documents are listed below and are hereby incorporated with their English specification and abstracts in their entireties.    1. Patent document No. 1: Japanese Patent Application Laid Open JP2012-064484    2. Patent document No. 2: US Patent Publication No. US-2011-0116253 (ST3001-0274)    3. Patent document No. 3: U.S. patent application Ser. No. 12/972,056 (ST3001-0280)
The disclosed subject matter has been devised to consider the above and other problems, characteristics and features. Thus, an embodiment of the disclosed subject matter can include semiconductor light source apparatuses which can emit various color lights having high brightness, and which can efficiently radiate a high heat generated by a phosphor layer from a radiating substrate via metallic bumps, even when a high power semiconductor light-emitting device is used under a large current as a light source. In this case, light emitted from a high power semiconductor light-emitting device can be efficiently wavelength-converted by the phosphor layer without a reduction of light intensity, because the phosphor layer is directly disposed on a reflective layer contacting with the metallic bumps mounted on the radiating substrate and does not include a substantially resin component.